Currently, a small base station, for example, radio access points such as a micro base station (Pico), a home base station (HeNB), a micro base station (Femto), and a relay base station (Relay), may be installed in a coverage of a Long Term Evolution (Long Term Evolution, LTE) macro base station (Macro eNB). In this way, a user equipment (User Equipment, UE) is covered by both the Macro eNB and the small base station, the maximum capacity achievable by such a system is a sum of the capacity of the Macro eNB and the capacity of the small base station, and the entire communications system has a higher capacity than a conventional LTE macro base station network. In scenarios such as office buildings, shopping malls and campus networks, heterogeneous deployments of the small base station and the macro base station can be used to enhance network coverage effectively and improve spectrum efficiency. The small base stations may access the network in a wired or wireless manner.
In such heterogeneous system, the UE can only be connected to one cell, where the cell is called a serving cell of the UE. Generally, a base station may have one or more cells. If the small base station and the macro base station are deployed by using the same frequency, all base stations send downlink signals on the same carrier, where the downlink signals include downlink control domain signals and downlink data domain signals. Inter-cell interference distribution increases with the increase of density and complexity of cells deployed under such heterogeneous system, and is difficult to predict. Meanwhile, a radio resource control (RRC) re-establishment procedure triggered by radio link failure caused by interference will also increase.
Referring to FIG. 1, FIG. 1 is a schematic diagram of a UE in a heterogeneous system scenario. For example, in a scenario of a heterogeneous system composed of a macro base station and small base stations in a coverage range of the macro base station, a cell covered by the macro base station is a macro cell, and a cell covered by the small base station is a low-power node cell. In the heterogeneous system, it is assumed that a rapidly moving UE keeps traversing multiple low-power node cells in the coverage range of the macro cell. A coverage area of the low-power node cell is relatively small, and a diameter of the cell is generally less than 100 m. For a rapidly moving UE, when the UE moves to a location near a center of the low-power node cell, signal quality of the low-power node cell is high enough for meeting conditions of handover from the macro cell to the low-power node cell. In this case, the macro base station determines to hand over the UE to the low-power node cell.
However, because the UE moves at a high speed, the UE will soon move into the coverage range of the macro cell outside the low-power node cell, whereupon the macro base station hands over the UE from the low-power node cell to the macro cell again. In this way, because the UE keeps traversing between multiple low-power node cells in the coverage range of the macro cell, the UE keeps handing over from the macro cell to the low-power node cell and handing over from the low-power node cell to the macro cell, which generates much signaling overhead.